spi: spi_mpc83xx clockrate fixes

This updates the SPI clock rate calculations for the spi_mpc83xx driver.
Some boundary conditions were wrong, and in several cases divide-by-16
wasn't always needed

Signed-off-by: Chen Gong <g.chen@freescale.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/spi/spi_mpc83xx.c b/drivers/spi/spi_mpc83xx.c
index 6832da6..070c621 100644 (file)
--- a/drivers/spi/spi_mpc83xx.c
+++ b/drivers/spi/spi_mpc83xx.c
@@ -266,21 +266,24 @@ int mpc83xx_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
 
        cs->hw_mode |= SPMODE_LEN(bits_per_word);
 
-       if ((mpc83xx_spi->spibrg / hz) >= 64) {
-               pm = mpc83xx_spi->spibrg / (hz * 64) - 1;
-               if (pm > 0x0f) {
-                       dev_err(&spi->dev, "Requested speed is too "
-                               "low: %d Hz. Will use %d Hz instead.\n",
-                               hz, mpc83xx_spi->spibrg / 1024);
-                       pm = 0x0f;
+       if ((mpc83xx_spi->spibrg / hz) > 64) {
+               pm = mpc83xx_spi->spibrg / (hz * 64);
+               if (pm > 16) {
+                       cs->hw_mode |= SPMODE_DIV16;
+                       pm /= 16;
+                       if (pm > 16) {
+                               dev_err(&spi->dev, "Requested speed is too "
+                                       "low: %d Hz. Will use %d Hz instead.\n",
+                                       hz, mpc83xx_spi->spibrg / 1024);
+                               pm = 16;
+                       }
                }
-               cs->hw_mode |= SPMODE_PM(pm) | SPMODE_DIV16;
-       } else {
+       } else
                pm = mpc83xx_spi->spibrg / (hz * 4);
-               if (pm)
-                       pm--;
-               cs->hw_mode |= SPMODE_PM(pm);
-       }
+       if (pm)
+               pm--;
+
+       cs->hw_mode |= SPMODE_PM(pm);
        regval =  mpc83xx_spi_read_reg(&mpc83xx_spi->base->mode);
        if (cs->hw_mode != regval) {
                unsigned long flags;